The Pro Micro is similar to the Pro Mini except with an ATmega32U4 on board instead of an ATmega328. The 32U4 has a USB transceiver built in, allowing USB connectivity on board. Thus the Pro Micro also adds a micro-USB connector.

This tiny board has familiar Arduino features: four channels of 10-bit ADC, five PWM pins, 12 DIOs, as well as hardware serial connections Rx and Tx.

This is the 5V version which runs at 16 MHz. There is a voltage regulator on board so it can accept voltage up to 12V DC. If you're supplying unregulated power to the board, be sure to connect to the RAW pin — not to VCC.

Board Dimensions: 1.3 × 0.7 inches.

Note: The micro-USB connector is soldered on the board — not through it. Be gentle when plugging and unplugging your USB cable. You might consider adding a dab of adhesive to strengthen the connector's bond with the PCB.